Effective anatomical and functional status of lower uterine segment at term: ultrasound evaluation in estimating risk of uterine dehiscence by ultrasound

OBJECTIVE: To define the role of lower uterine segment (LUS) evaluation at term.
DESIGN:
Observational case-control study.
SETTING:
University hospital.
PATIENT(S):
Ninety-four patients were divided into two groups. Group A consisted of 45 multiparous single fetus pregnant women with up to two previous cesarean sections (CS). Group B consisted of 49 multiparous pregnant women with up to three vaginal deliveries and no uterine scars.
INTERVENTION(S):
Total LUS and myometrial thickness were measured by sonogram in all patients before undergoing a CS.
MAIN OUTCOME MEASURE(S):
The primary outcome is a correlation between echographic measurements and features of the LUS at the time of CS. The secondary outcome is a definition of a correlation between the number of previous CS, interdelivery interval time, and features of the LUS (grades I-IV).
RESULT(S):
Sonographic measurements revealed significant differences in LUS size and myometrial thickness between the two groups. Grades III and IV of LUS were only observed in group A. An interdelivery interval <18 months, LUS thickness ≤3.0 mm, and myometrial thickness <1.5 mm were statistically significant predictors of LUS grades III and IV. Number of previous CS showed no correlation with surgical LUS status.
CONCLUSION(S):
Sonographic evaluation of the LUS may be a noninvasive, reproducible, and safe technique for defining the risk of uterine dehiscence, with a sensitivity of 100% and specificity of 85% (positive predictive value, 45%; negative predictive value, 100%).